1. Field of the Invention
The present general inventive concept relates to an inkjet printhead, and more particularly, to an inkjet printhead in which a water repellent layer is formed on a nozzle plate.
2. Description of the Related Art
Ink-ejection methods of an inkjet printer can be classified into an electro-thermal transducer method, which is also called a bubble jet method, and an electro-mechanical transducer method. In the electro-thermal transducer method, a heat source is used to generate bubbles in ink and the ink is ejected using a force generated by the bubbles. In the electro-mechanical transducer method, ink is ejected using a piezoelectric material, wherein the ink is ejected according to a change in volume of the ink caused by a deformation of the piezoelectric material.
In the electro-thermal transducer method, a heater is mounted in a chamber of a printhead to supply heat and a considerably large amount of heat energy is supplied during a very short time period, and thus heat is generated due to the resistance characteristics of the heater. The heat is transferred to the ink that is contacting the heater, and thus the temperature of the water-soluble ink is increased above the boiling point of the ink. When the temperature of the ink is increased above the boiling point, bubbles are formed, and these bubbles pressurize the ink around the bubbles. The pressurized ink is ejected through nozzles due to the difference between the atmospheric pressure and the pressure of the ink. While being ejected onto the paper, the ink forms ink droplets in order to minimize the surface energy of the ink itself.
In the electro-mechanical transducer method, a piezoelectric material is attached to a diaphragm to pressurize a chamber of a printhead. Pressure is provided to a chamber to eject the ink using the piezoelectric characteristic of generating force when a voltage is applied. Thus force is generated according to the applied voltage to transfer pressure into the chamber.
An inkjet printhead includes a nozzle plate having a plurality of nozzles to eject ink. The nozzle plate can be formed of photosensitive epoxy resin using a photolithography method and has a hydrophilic external surface having a contact angle of about 66 degrees.
When the ink is ejected out through the nozzle, ink droplets commonly contaminate areas around the nozzle, which prevents the formation of desired ink droplets and adversely affects the ability of the nozzle to maintain a desired uniform ejection direction of the ink droplets.
Further, if ink contaminates areas around the nozzle after the ink droplets are ejected, the remaining ink may be undesirably transferred to and otherwise contaminate a printing medium, thereby decreasing a printing quality.